The present invention relates to a disc player for recording information into and reproducing information from an optical disc, in particular to a disc player having an adjustment mechanism for adjusting a positional relationship between an optical pickup and a turntable within the disc player.
Conventionally, an optical pickup of a disc player is used to converge a laser beam onto an optical disc so as to record a great amount of information on the recording surface of an optical disc. Meanwhile, with the use of the optical pickup, a reflected light from the optical disc is directed and converged onto a photodetector so as to reproduce the information previously recorded on the optical disc.
The above optical disc is mounted on a turntable. which is driven by a spindle motor provided within the disc player. In order to ensure a correct information recording and information reproducing, it is necessary to perform a tracking control so that a laser beam may constantly trace an information track formed on the recording surface of an optical disc. During such tracking control, a laser beam from a laser diode is divided by an optical element (called grating) into one main-beam and two sub-beams. The two sub-beams are directed to the information recording surface of an optical disc at an inclined angle with respect to a tangential line of an information track. Then, two reflected lights from the optical disc are detected by two photodetectors so as to produce a difference between two outputs from the two photodetectors, thereby enabling a desired tracking control for both the information recording and the information reproducing.
However, with a disc player having a servo system in which the position of an optical pickup is movable in a radial direction of an optical disc, the position of the grating within the optical pickup is apt to deviate from the radial line direction, due to some unavoidable precision errors possibly caused in an assembling process for assembling a disc player. As a result, a tangential direction of an information track and the two sub-beams are likely to deviate from predetermined angles, making it impossible to perform a correct tracking control. For this reason, it is necessary to provide an adjusting system for correcting the above-discussed deviations.
A first example for the above adjustment may be achieved by adjusting a lens position in an optical pickup, so that the optical pickup may exactly trace along the radial direction of an optical disc.
A second example for the above adjustment is not to adjust a lens position in an optical pickup, instead, a fixing screw for adjusting a spindle motor is loosened to adjust the position of said spindle motor, so as to enable the optical pickup to exactly trace in the radial direction of an optical disc. Upon completion of such adjustment, the fixing screw is again screwed up, thereby enabling the said spindle motor to be secured in a correct position.
However, with the above first example according to a prior art, it is necessary that all the elements for forming the servo system be made with a high precision in size and that an assembling operation for attaching the servo system to the disc player be conducted with a high assembling precision. Further, even if people could try to make all the elements (for forming the servo system) with a high precision, some sorts of size errors are in fact difficult to avoid, hence making it indispensable to perform fine adjustment for the optical pickup.
On the other hand, with the above second example according to a prior art, the positional adjustment between the disc information recording surface and the optical pickup should be completed not only by adjusting the positions of the spindle motor and the turntable, but also by adjusting the optical disc in very direction in order to eliminate all kinds of possible inclinations. As a result, the adjustment operation is troublesome and time consuming.